Now we're gonna talk about feedback loops in the body. We're gonna do this because homeostasis is largely controlled through feedback loops. A feedback loop is gonna occur when a change to the internal environment causes a response. And that response is the feedback part and the response is gonna alter the internal environment. So if you remember where we started though, we started with a change to the internal environment, we're back at the beginning. That's the loop. There's gonna be two types of feedback loops that we're gonna talk about first is negative, negative feedback loops, move the system in the opposite direction to the original stimulus. In contrast, positive feedback loops move the system in the same direction is the original stimulus. All right, we're gonna look at both of these in a little bit more detail here. Let's start with negative feedback, negative feedbacks, moves the system towards the set point and that maintains homeostasis. That's why we're talking about this one first and we're gonna go into it in a lot more detail in upcoming videos. We are concerned with maintaining homeostasis because that's gonna be one of the major things that happens in physiology. In the body. So if we see our set point here on this little dial, we have a little dial and the arrow is pointing up and it looks like it's falling off to the right here. Well, negative feedback is gonna move the system towards the set point in the opposite direction of the stimulus. So it is gonna push this dial back up to where it started. I like to think of this as a person balancing on one leg. And so we have a little image of someone balancing on one leg here to remind you of that homeostasis, we said is standing still in one place, but it's a dynamic process. If you're standing on one leg, you might look kind of stable, but there's all sorts of negative feedback going on. If you lean forward, your body pushes a little bit back because you can lean one way, you stick your arms out to fix your balance and you come back to the center, all of your movements are gonna be opposite the stimulus so that you return to your set point. This means that negative feedback is kind of self regulating. It's, it turns itself off, it gets back to the, to the set point and it's all set. It also means it's gonna be more common in the body. And again, we're trying to maintain homeostasis, we're trying to stay at set points. Negative feedback is really good at that. In contrast, we have positive feedback, positive feedback moves the system away from the set point. So we have our little dial here and we have our set point up the middle. And you can imagine if the set point falls off to one side, what positive feedback is gonna do is just gonna keep pushing it farther and farther and farther in the same direction. I like to think of this with the analogy of a fire. When you start a fire, you light some paper, it generates heat, the more heat it generates, the more things catch on fire, the more things that catch on fire, the more heat it generates and the fire just gets bigger and bigger and bigger, just like positive feedback. Now, importantly, this requires sort of an off switch in the body. You don't want these positive feedback systems getting out of control and they have the potential to, it also means they're gonna be a little bit less common or rather a lot less common because moving away from the set point. Well, that's not what we want to do if we're maintaining homeostasis. The last thing that I want to note here is that a misconception some people have, when we say negative, we often think on like a number line, it means going less than negative feedback could push something in a positive or negative direction. It just depends on what the original stimulus was negative. In this case means opposite, same thing for positive. Normally you think on a number line, positive means more. Well, positive feedback just means in the same direction, it could be that something is getting less and then positive feedback just makes it get less and less and less continually. All right with that in mind, as I said, we're gonna look at negative feedback in a lot of detail and we'll look at positive feedback in some detail as well coming up and I'll see you there.
